Such laboratory tempering devices are used for the cyclic tempering of reaction samples to different temperatures, as required for example, for carrying out some biochemical reactions. PCR (polymerase chain reaction) is one of the main areas of application of such tempering devices. If the optimum temperatures of the respective temperature areas are known, a large number of samples may be processed in one pass of several cycles even for large-scale throughputs. The expression “pass” is understood to be a closed reaction pass in which the sequence of steps was repeated several times. However, the optimum temperatures of the individual temperature areas must be determined before large-scale through-puts are possible.
Laboratory tempering devices, as known, for example, from U.S. Pat. No. 6,054,263 and DE 196 46 115 A1, bring all samples to different temperatures within the assigned temperature area in one step of the cyclically repeated sequence of steps. When the reaction results are evaluated, it is possible to ascertain the samples for which an optimum result is obtained in a step. This is then the optimum temperature for such step.
In conventional commercial, laboratory tempering devices, the samples are disposed in rows and columns in a two-dimensional array. The temperature differences are applied as a gradient in one direction over the array. The sequence of steps is repeated cyclically. In the case of these so-called gradient cycles, different temperatures are employed only for the same step during each cyclically repeated sequence of steps. Therefore, only the temperature for one step can be optimized in one pass and several passes are required for optimizing the temperatures of all steps. This is associated with the expenditure of much time and the consumption of expensive samples.
It has been proposed in DE 196 46 115 A1 to apply gradients in the X and Y directions in two steps in each sequence of steps. With that, two steps can be optimized in each pass. However, if the sequence of steps consists of more steps, such as the conventional three steps of the standard PCR process, then the further steps must be optimized in separated passes. In addition, for designing gradients in different directions, increased expenditures for equipment and evaluation is required.